var origDefineProperty = Object.defineProperty;

var arePropertyDescriptorsSupported = function() {
  var obj = {};
  try {
    origDefineProperty(obj, "x", { enumerable: false, value: obj });
    for (var _ in obj) {
      return false;
    }
    return obj.x === obj;
  } catch (e) {
    /* this is IE 8. */
    return false;
  }
};
var supportsDescriptors =
  origDefineProperty && arePropertyDescriptorsSupported();

if (!supportsDescriptors) {
  Object.defineProperty = function(a, b, c) {
    //IE8支持修改元素节点的属性
    if (origDefineProperty && a.nodeType == 1) {
      return origDefineProperty(a, b, c);
    } else {
      a[b] = c.value || (c.get && c.get());
    }
  };
}

alert(111)